1. Field of the Invention
The present invention relates to a method of improving the aroma and flavor of coffee using noble gases.
2. Description of the Background
Coffee is cultivated in many tropical countries and the beans afford a soothing drink which may be both relaxing and stimulating. Coffee beans generally constitute about 1-2% caffeine, 10-15% coffee oil, 8% of sugars, such as sucrose, 11% proteins, 5% ash and 6% chlorogenic and caffeic acid. Other constituents include cellulose, hemicelluloses, trigonelline, tannic acid and volatile oils. Merck Index (11th edition).
Coffee processing involves the various following steps, some of them being optional:
picking of green coffee beans, their packaging in hemp bags,
transport, blending
cleaning
roasting
stoning/cleaning
grinding (optional)
packaging of roast beans or ground roast coffee (optional)
preparation of dried instant coffee from ground roast (optional)
packaging of dried instant coffee (optional)
The freshness of coffee is known to be compromised by several factors, including the escape of volatiles and oxygen-induced polymerization of flavor constituents.
Coffee is currently packaged under nitrogen or under vacuum in order to protect its components from contact with oxygen. The coffee roasting and grinding process is described in Sivetz and Desrosier, Physical and Chemical Aspects of Coffee (AVI Publishing Company, Inc.) (1979), and involves essentially batch or onstream roasting, followed by grinding, followed by storage. At every stage, it is possible to impose an inert atmosphere to protect the coffee, but generally, this is done only upon packaging and storage.
For example, CH 573848 describes the inerting activity of nitrogen in preparation of packaged coffee.
WO 8600503, DE 3425088, AU 8546026, EP 189442 and DE 3448380 each discloses the use of gas in the heating of coffee products to prevent the loss of aroma and prevent boiling, wherein nitrogen and or noble gases are considered equivalent.
FR 2225095 describes packaging of roasted coffee under a gas atmosphere wherein the coffee is degassed with an inert gas for 12 to 48 hours, then impermeable packets are filled with the roasted coffee, a 50-90% partial vacuum is drawn, followed by injection of a preservative gas, where either argon or nitrogen are used, with no different effect reported (nitrogen and argon are used with equivalence).
In fact, changes in the chemical composition of coffee headspace caused by oxidation are one of the main factors responsible for quality loss in coffee as either roasted beans or grounds. Exposure of coffee to air causes rapid staling. Staleness caused by oxidation can be detected by simple tasting, when compared to a freshly ground coffee. Staling of coffee grounds is five to ten times faster than that of coffee beans. See Food Chemistry, 36:135-148, Kallio et al.
Coffee aroma and flavor are of complex and unstable composition. Over 700 compounds have been reported and identified as coffee headspace volatiles. A typical gas chromatogram of the headspace from brewed coffee is given by Shimoda et al., J. Agric. Food. Chem., 38:802-804, 1990. Sixty-two compounds were found and identified. These are aldehydes, ketones, esters, pyrazines, mercaptans, sulfides, disulfides, thiophenes, and thiazoles. The major coffee volatile was 2-methylbutanal (GC area %=17.7).
Studies using gas chromatography and mass spectrometry show that about 50% aldehydes, 20% ketones, 8% esters, 7% heterocyclic, 2% dimethyl sulfide, and lesser amounts of other organic and odorous sulfides constitute the body of coffee aroma volatiles. Contributing to a lesser extent to the coffee aroma are also nitriles, alcohols, low molecular weight saturated and unsaturated hydrocarbons, furans, furfurals, and acetic acid. Particularly important in defining the coffee aroma are acetaldehyde, diacetyl, and dimethyl sulfide; the latter being defined as an exhilarating constituent of the coffee aroma.
An example of a coffee headspace chromatogram in an air atmosphere is given by Kallio et al, 1990. Thirty-eight compounds were found and identified. Oxidation in air-packaged coffee can be traced by the disappearance of carbon disulfide, dimethyl sulfide and dimethyl disulfide peaks. The oxidation of the strong aromatic constituent dimethyl sulfide to the nonvolatile and odorless methyl sulfoxide is one of the main contributors to coffee flavor deterioration. Methyl sulfoxide can also undergo further oxidation. Aldehydes, which constitute the bulk of coffee volatiles, are also readily susceptible to oxidation. Ratios of volatiles are also useful indicators of deterioration due to oxidation. For example, the ratio of 2-methylfuran/2-butanone (M/B), one of the coffee aroma indexes (Kallio et al., 1990), decreases in the presence of air due to oxidation, as demonstrated by GC/MS headspace analysis.
Oxidation can also lead to certain chemical reactions between coffee solubles and coffee volatiles. Moisture in air also contributes to the deteriorating effect of oxygen on coffee flavor.
Roast coffee beans and grounds are currently packaged or otherwise stored in air-tight containers under vacuum or a protective inert atmosphere to prevent oxidation. However, these methods are not completely effective, and address only oxidations driven by the presence of atmospheric oxygen. Further, nitrogen does not completely displace oxygen, and vacuum packaging removes a portion of the desirable flavor components.
Hence, a need exists for a method by which both the aroma and flavor of coffee may be improved during either production or storage or both.
It is an object of the present invention to provide a method of improving the aroma and/or the flavor of coffee by direct chemical control.
It is an object of the present invention to provide a method of improving the aroma and/or the flavor of coffee using certain noble gases.
It is a further object of the present invention to improve the shelf life of said coffee.